1. Field of the Invention
The present invention relates to a content processing apparatus. More specifically, the present invention relates to a content processing apparatus that restricts an available period of a content.
2. Description of the Prior Art
These days, there is an increasing need for assigning a period of seven days, thirty days or the like to each of contents such as image data, audio data and computer software in order to impose an available-period restriction with which the content becomes unavailable after this period has passed since a first using time. For situations requiring the available-period restriction, for example, there are a case of charging for a content in providing it according to an available period and a case of restricting a storage period of a recorded image from a surveillance camera in recording it from a viewpoint of human rights protection, etc.
A prior art for applying the available period restriction as mentioned above is disclosed in Japanese Patent Laying-open No. H8-212115 laid-open on Aug. 20, 1996. According to this prior art, image files are stored in a hard disk (HD). A storage period is assigned to each of the image files, and, after the storage period has elapsed, the image file is deleted from the HD or is once read out from the HD, subjected to a compression process and an image quality degradation process, and stored again in the HD. Due to this, the image file whose available period has passed, cannot be reproduced at all or can be reproduced but viewed only with low image quality.
In the above prior art, however, whenever an image file whose available period has passed, comes into existence, it is necessary to perform a heavy process such as deleting or compressing the relevant image file. Thus, a heavy load is imposed especially in a case where a large number of files are handled.